Multi-image display apparatus including polarization selective lens and screen

ABSTRACT

Provided is a multi-image display apparatus including an image forming device configured to form a first image, a first polarization plate configured to transmit a first polarization component of the first image provided from the image forming device, a second polarization plate configured to transmit a second polarization component of a second image that is provided from a path different from the first image, the second polarization component being different from the first polarization component, a screen configured to reflect and diffuse the first image, and transmit the second image, and a polarization selective lens configured to focus the first image having the first polarization component, and transmit the second image having the second polarization component without refraction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. application Ser.No. 16/591,152, filed Oct. 2, 2019 in the United States Patent andTrademark Office, which claims priority from Korean Patent ApplicationNo. 10-2018-0145645, filed on Nov. 22, 2018 in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein intheir entireties by reference.

BACKGROUND 1. Field

Example embodiments of the present disclosure relate to a multi-imagedisplay apparatus such as an augmented reality system, and moreparticularly, to a multi-image display apparatus providing a wide angleof view using a polarization selective lens and screen while the size ofthe multi-image display apparatus is reduced or miniaturized.

2. Description of the Related Art

Recently, along with the development of electronic apparatuses anddisplay apparatuses capable of implementing virtual reality (VR),interest in such apparatuses has increased. As a next step of VR,technology for implementing augmented reality (AR) and mixed reality(MR) is being researched.

Unlike VR that is based on a complete virtual world, AR is a displaytechnique that shows the real world and overlapped or combined virtualobjects or information thereon, thereby further increasing the effect ofreality. While VR is limitedly applied only to fields such as games orvirtual experience, AR is advantageous in that it may be applied tovarious real environments. In particular, AR attracts attention asnext-generation display technology suitable for a ubiquitous environmentor an Internet of things (IoT) environment. AR may be an example of MRin that it shows a mixture of the real world and additional informationsuch as virtual world.

SUMMARY

One or more example embodiments provide a multi-image display apparatussuch as an augmented reality system.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of example embodiments.

According to an aspect of an example embodiment, there is provided amulti-image display apparatus including an image forming deviceconfigured to form a first image, a first polarization plate configuredto transmit a first polarization component of the first image providedfrom the image forming device, a second polarization plate configured totransmit a second polarization component of a second image that isprovided from a path different from the first image, the secondpolarization component being different from the first polarizationcomponent, a screen configured to reflect and diffuse the first image,and transmit the second image, and a polarization selective lensconfigured to focus the first image having the first polarizationcomponent, and transmit the second image having the second polarizationcomponent without refraction.

The screen may include a first surface and a second surface that isopposite to the first surface, and the screen may further include ananisotropic holographic screen configured to reflect and diffuse lightthat is incident on the first surface at an angle, and transmit lightincident on the second surface.

The image forming device may be disposed to provide the first image tothe first surface of the screen at an angle.

The second polarization plate may be disposed on the second surface ofthe screen.

The screen may be configured such that a diffusion central angle is 0degrees from a normal line perpendicular to the first surface in acentral area of the first surface, and the diffusion central angleincreases from the normal line perpendicular to the first surface fromthe central area of the first surface to edge areas of the firstsurface.

The screen may be configured such that the diffusion central angle issymmetrically inclined based on the central area of the first surface,and light reflected and diffused at the diffusion central angle from thefirst surface are gathered on a point of an optical axis.

The diffusion central angle may range from 10 degrees to 20 degrees atan edge of the first surface.

The multi-image display apparatus, wherein a diffusion angle at whichlight is reflected and diffused from the first surface is within 10degrees.

The first image may include a first color image, a second color image,and a third color image, and the screen may include a first anisotropicholographic screen configured to reflect and diffuse the first colorimage that is incident on a first surface of the first anisotropicholographic screen at an angle, and transmit light incident on a secondsurface of the first anisotropic holographic screen that is opposite tothe first surface, a second anisotropic holographic screen configured toreflect and diffuse the second color image that is incident on a thirdsurface of the second anisotropic holographic screen at an angle, andtransmit light incident on a fourth surface of the second anisotropicholographic screen that is opposite to the third surface, and a thirdanisotropic holographic screen configured to reflect and diffuse thethird color image that is incident on a fifth surface of the thirdanisotropic holographic screen at an angle, and transmit light incidenton a sixth surface of the third anisotropic holographic screen that isopposite to the fifth surface.

The image forming device may be configured to provide the first colorimage to the first surface of the first anisotropic holographic screenat an angle, provide the second color image to the third surface of thesecond anisotropic holographic screen at an angle, and provide the thirdcolor image to the fifth surface of the third anisotropic holographicscreen at an angle.

The first anisotropic holographic screen may be configured to transmitthe second color image and the third color image incident on the firstsurface, the second anisotropic holographic screen is configured totransmit the first color image and the third color image incident on thethird surface, and the third anisotropic holographic screen isconfigured to transmit the first color image and the second color imageincident on the fifth surface.

The first anisotropic holographic screen may be configured such that adiffusion central angle of the first color image is 0 degrees from anormal line perpendicular to the first surface, in a central area of thefirst surface, and the diffusion central angle of the first color imagefrom the normal line perpendicular to the first surface increases fromthe central area of the first surface to edge areas of the firstsurface, the second anisotropic holographic screen is configured suchthat a diffusion central angle of the second color image is 0 degreesfrom a normal line perpendicular to the third surface in a central areaof the third surface, and the diffusion central angle of the secondcolor image from the normal line perpendicular to the third surfaceincreases from the central area of the third surface to edge areas ofthe third surface, and the third anisotropic holographic screen isconfigured such that a diffusion central angle of the third color imageis 0 degrees from a normal line perpendicular to the fifth surface in acentral area of the fifth surface, and the diffusion central angle ofthe third color image from the normal line perpendicular to the fifthsurface increases from the central area of the fifth surface to edgeareas of the fifth surface.

The first anisotropic holographic screen, the second anisotropicholographic screen, and the third anisotropic holographic screen may besequentially disposed away from the polarization selective lens, suchthat the first color image has a first light path length, the secondcolor image has a second light path length greater than the first lightpath length, and the third color image has a third light path lengthgreater than the second light path length, and the first anisotropicholographic screen, the second anisotropic holographic screen, and thethird anisotropic holographic screen are disposed to offset chromaticaberration of the polarization selective lens.

The multi-image display apparatus may further include a light guideplate disposed between the screen and the polarization selective lens.

The light guide plate may include an input coupler configured to reflectincident light at an angle, and to provide the incident light into thelight guide plate, and the image forming device may be disposed toprovide the first image to the input coupler of the light guide plate.

The light guide plate may be configured to totally reflect the firstimage provided at an angle to the light guide plate by the inputcoupler, between a first surface of the light guide plate and a secondsurface of the light guide plate that is opposite to the first of thelight guide plate, and the screen is directly disposed on the firstsurface of the light guide plate.

The polarization selective lens may be configured to focus light havinga first circular polarization component having a first rotationdirection and transmit, without change, light having a second circularpolarization component having a second rotation direction which isopposite to the first rotation direction.

The polarization selective lens may include two geometric phase lensesand a polarization conversion plate between the two geometric phaselenses, the two geometric phase lenses may be configured to operate asconvex lenses with respect to the light having the first circularpolarization component, and operate as concave lenses with respect tothe light having the second circular polarization component, and thepolarization conversion plate may be configured to transmit, withoutchange, the light having the first circular polarization component, andconvert the light having the second circular polarization component intothe light having the first circular polarization component.

The first polarization plate may include a first circular polarizationplate configured to transmit the light having the first circularpolarization component, and the second polarization plate includes asecond circular polarization plate configured to transmit the lighthaving the second circular polarization component.

The screen may include a polarization selective screen configured toreflect and diffuse light having a first linear polarization component,and transmit light having a second linear polarization component that isperpendicular to the first linear polarization component, the firstpolarization plate may include a first linear polarization plateconfigured to transmit the light having the first linear polarizationcomponent, and the second polarization plate includes a second linearpolarization plate configured to transmit the light having the secondlinear polarization component perpendicular to the first linearpolarization component, and the multi-image display apparatus mayfurther include a ¼ wavelength plate disposed between the screen and thepolarization selective lens.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings in which:

FIG. 1 is a schematic view illustrating a configuration of a multi-imagedisplay apparatus according to an example embodiment;

FIGS. 2 and 3 are schematic cross-sectional views illustrating anexample configuration and operation of a polarization selective lens ofthe multi-image display apparatus illustrated in FIG. 1 ;

FIG. 4 is a schematic cross-sectional view illustrating an operation ofan anisotropic holographic screen of the multi-image display apparatusillustrated in FIG. 1 ;

FIGS. 5 and 6 are schematic cross-sectional views illustratingoperations of related diffusion screens;

FIGS. 7 through 10 are schematic views illustrating a configuration formanufacturing an anisotropic holographic screen of the multi-imagedisplay apparatus illustrated in FIG. 1 ;

FIG. 11 is a schematic view illustrating a configuration of amulti-image display apparatus according to an example embodiment;

FIGS. 12 through 14 are schematic views illustrating a configuration formanufacturing wavelength-selective anisotropic holographic screens ofthe multi-image display apparatus illustrated in FIG. 11 ;

FIG. 15 is a schematic view illustrating a configuration of amulti-image display apparatus according to an example embodiment;

FIGS. 16A and 16B are schematic views illustrating a configuration of amulti-image display apparatus according to an example embodiment;

FIG. 17 is a schematic view illustrating a configuration of amulti-image display apparatus according to an example embodiment;

FIGS. 18 and 19 are schematic views illustrating an operation of apolarization selective screen illustrated in FIG. 17 ;

FIG. 20 is a schematic view illustrating a configuration of amulti-image display apparatus according to an example embodiment; and

FIGS. 21 through 23 are views illustrating various electronic devices towhich a multi-image display apparatus is applicable according to exampleembodiments.

DETAILED DESCRIPTION

Hereinafter, multi-image display apparatuses including a polarizationselective lens and a screen will be described with reference to theaccompanying drawings. In the drawings, like reference numerals refer tolike elements, and the sizes of elements may be exaggerated for clarityof illustration. Example embodiments described herein are forillustrative purposes only, and various modifications may be madetherefrom. In the following description, when an element is referred toas being “above” or “on” another element in a layered structure, it maybe directly on an upper, lower, left, or right side of the other elementwhile making contact with the other element or may be above an upper,lower, left, or right side of the other element without making contactwith the other element.

It will be understood that the terms “comprise” or “include” should notbe construed as including all elements or steps described in thespecification and may omit some elements or some steps or may furtherinclude additional elements or steps. While such terms as “first”,“second”, etc., may be used to describe various components, suchcomponents must not be limited to the above terms. The above terms areused only to distinguish one component from another.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of”, when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list. Forexample, the expression, “at least one of a, b, and c,” should beunderstood as including only a, only b, only c, both a and b, both a andc, both b and c, or all of a, b, and c.

FIG. 1 is a schematic view illustrating a configuration of a multi-imagedisplay apparatus 100 according to an example embodiment. Referring toFIG. 1 , the multi-image display apparatus 100 according to the exampleembodiment may include an image forming device 110 configured to form afirst image L10, an anisotropic holographic screen 140 configured toreflect and diffuse the first image L10 and transmit a second image L20,and a polarization selective lens 160 configured to focus the firstimage L10 and transmit the second image L20 without refraction. Also,the multi-image display apparatus 100 may further include a collimatinglens 130 configured to collimate the first image L10 formed by the imageforming device 110 and provide the collimated first image L10 to theanisotropic holographic screen 140. When the image forming device 110provides an image that is collimated, the collimating lens 130 may beomitted.

For example, the first image L10 may be a display image formed andprovided by the image forming device 110 in the multi-image displayapparatus 100 and may contain virtual reality or virtual information.The second image L20 may be an image of the outside that a user faces.The second image L20 may include an image of a foreground that the userfaces, and a background subject. The second image L20 may be an image ofthe real world. Therefore, the multi-image display apparatus 100 of theexample embodiment may be used for implementing augmented reality (AR)or mixed reality (MR). In this case, the multi-image display apparatus100 may be a near-eye AR display apparatus.

The image forming device 110 forming the first image L10 may beconfigured in various ways. For example, the image forming device 110may include a light source and a spatial light modulator. For example,the spatial light modulator may include a semiconductor modulator basedon a compound semiconductor such as GaAs, a liquid crystal on silicon(LCoS) panel, a liquid crystal display (LCD) panel, a digital lightprojection (DLP) panel, or the like. The image forming device 110 mayform the first image L10 using the light source and the spatial lightmodulator. The light source may, for example, include a plurality oflight-emitting diodes or a plurality of laser diodes capable of emittingred light, green light, and blue light, respectively. Therefore, thefirst image L10 formed by the image forming device 110 may include a redimage, a green image, and a blue image.

As an example, the image forming device 110 may include a display panel.For example, the display panel may include a micro light-emitting diode(LED) display panel, an organic LED (OLED) display panel, or a liquidcrystal display (LCD) display panel. The first image L10 realized byusing the display panel may be a two-dimensional (2D) image or athree-dimensional (3D) image. For example, the 3D image may be ahologram image, a stereo image, a light field image, an integralphotography (IP) image, etc.

The polarization selective lens 160 is configured to focus incidentlight or transmit the incident light without refraction based on apolarization state of the incident light. For example, the polarizationselective lens 160 may focus light having a first circular polarizationcomponent having a first rotation direction and may intactly transmitlight having a second circular polarization component having a secondrotation direction without change, which is a direction opposite to thefirst rotation direction. Thus, when the first image L10 formed by theimage forming device 110 has the first circular polarization component,the polarization selective lens 160 may provide the first image L10 to auser's eye by focusing the first image L10. Also, when the second imageL20, which is an image of the real world, has the second circularpolarization component, the polarization selective lens 160 may providethe second image L20 to the user's eye without change and distortion.

To this end, the multi-image display apparatus 100 may further include afirst circular polarization plate 120 for transmitting only the lighthaving the first circular polarization component and a second circularpolarization plate 150 for transmitting only the light having the secondcircular polarization component. The first circular polarization plate120 is arranged on a light path of the first image L10, the light pathbeing between the image forming device 110 and a first surface 141 ofthe anisotropic holographic screen 140, so that the first image L10incident on the polarization selective lens 160 has the first circularpolarization component. The second circular polarization plate 150 isarranged to face a second surface 142 of the anisotropic holographicscreen 140 so that the second image L20 incident on the polarizationselective lens 160 has the second circular polarization component.

The polarization selective lens 160 may be configured in various ways.For example, FIGS. 2 and 3 are schematic cross-sectional viewsillustrating an example configuration and operation of the polarizationselective lens 160 of the multi-image display apparatus 100 illustratedin FIG. 1 . Referring to FIGS. 2 and 3 , the polarization selective lens160 may include two identical geometric phase lenses 160 a and 160 c anda polarization conversion plate 160 b between the two same geometricphase lenses 160 a and 160 c. The geometric phase lenses 160 a and 160 care optical devices operating as convex lenses or concave lenses, basedon a polarization characteristic of incident light. For example, thegeometric phase lenses 160 a and 160 c may operate as convex lenseshaving a focal distance f with respect to the light having the firstcircular polarization component and may operate as concave lenses havinga focal distance f with respect to the light having the second circularpolarization component. Also, the geometric phase lenses 160 a and 160 cmay change a polarization direction of transmitted light into theopposite direction. The polarization conversion plate 160 b operates tointactly transmit the light having the first circular polarizationcomponent without change and to convert the light having the secondcircular polarization component into the light having the first circularpolarization component. The polarization conversion plate 160 b may beformed to be very thin, and thus, when the polarization selective lens160 is formed, the polarization conversion plate 160 b may be coupledbetween the two geometric phase lenses 160 a and 160 c.

When the first image L10 having the first circular polarizationcomponent is incident on the polarization selective lens 160, thegeometric phase lens 160 a may act as a convex lens to the first imageL10 and change a polarization state of the first image L10 to the secondcircular polarization component, as illustrated in FIG. 2 . Then, thepolarization state of the first image L10 may change back to the firstcircular polarization component again, by passing through thepolarization conversion plate 160 b. Then, the geometric phase lens 160c may act as a convex lens to the first image L10 and change thepolarization state of the first image L10 to the second circularpolarization component. The polarization selective lens 160 may changethe polarization state of the first image L10 from the first circularpolarization state to the second circular polarization state. Since thepolarization conversion plate 160 b is very thin, it may be understoodthat the two geometric phase lenses 160 a and 160 c of the polarizationselective lens 160 substantially adhere to each other. When the twoconvex lenses adhere to each other, the focal distance reduces twice,and thus, the polarization selective lens 160 may operate as the convexlens having half of a focal distance with respect to the first image L10having the first circular polarization component than each of thegeometric phase lenses 160 a and 160 c, with respect to the first imageL10 having the first circular polarization component.

Also, when the second image L20 having the second circular polarizationcomponent is incident on the polarization selective lens 160, thegeometric phase lens 160 a may act as a concave lens to the second imageL20 and change a polarization state of the second image L20 to the firstcircular polarization component. The second image L20 that has the firstcircular polarization component may maintain the first circularpolarization component by passing through the polarization conversionplate 160 b. Then, the geometric phase lens 160 c may act as a convexlens to the second image L20 and change the polarization state of thesecond image L20 to the second circular polarization component.Consequently, since the second image L20 passes through each of theconcave lens and the convex lens once, the concave lens and the convexlens having the same focal distance, no optical effect may be applied tothe second image L20 by passing through the polarization selective lens160. Accordingly, the second image L20 having the second circularpolarization component may pass through the polarization selective lens160 without change and distortion.

The polarization selective lens 160 may have other configurations thanthe configuration described in FIGS. 2 and 3 . For example, thepolarization selective lens 160 may be configured by singularly using ageometric phase lens, a meta lens, a double refraction lens, adiffraction lens, etc., which have artificially designed minutediffractive patterns, or may be configured by combining at least twothereof.

The anisotropic holographic screen 140 includes the first surface 141and the second surface 142 opposite to each other. The first surface 141of the anisotropic holographic screen 140 is arranged toward thepolarization selective lens 160 and the second surface 142 thereof isarranged toward the second circular polarization plate 150. Also, theimage forming device 110 is arranged such that the first image L10 isincident into the first surface 141 of the anisotropic holographicscreen 140 and the second image L20 is incident into the second surface142 of the anisotropic holographic screen 140.

The anisotropic holographic screen 140 is configured to reflect anddiffuse light incident into the first surface 141 and to intactlytransmit light incident into the second surface 142. Thus, theanisotropic holographic screen 140 may operate as a screen for the firstimage L10 incident into the first surface 141, while functioning as atransparent flat plate for the second image L20 incident into the secondsurface 142.

In particular, the anisotropic holographic screen 140 may be configuredto have different diffusion central angles based on a location of thefirst surface 141, on which the light is incident. For example, FIG. 4is a schematic cross-sectional view illustrating an operation of theanisotropic holographic screen 140 of the multi-image display apparatus100 illustrated in FIG. 1 . Referring to FIG. 4 , in a central area ofthe anisotropic holographic screen 140, the diffusion central angle β isapproximately 0 degrees with respect to a normal line perpendicular tothe first surface 141. For example, in the central area of theanisotropic holographic screen 140, the diffusion central angle β isperpendicular to the first surface 141. Here, the diffusion centralangle β is an angle, which is the middle of a range of angles, at whichlight is reflected and diffused from a point on the first surface 141 ofthe anisotropic holographic screen 140. A ray reflected and diffused atthe diffusion central angle β has the greatest intensity from among raysreflected and diffused from a point on the first surface 141 of theanisotropic holographic screen 140.

Meanwhile, the diffusion central angle β may have a greater inclinationwith respect to the normal line perpendicular to the first surface 141,as a distance from the center of the first surface 141 of theanisotropic holographic screen 140 increases. Also, as illustrated inFIG. 4 , the diffusion central angle β may be symmetrically inclinedbased on the center of the first surface 141 of the anisotropicholographic screen 140. Thus, the anisotropic holographic screen 140 maybe configured such that light reflected/diffused at the centraldiffusion angle β from all points on the first surface 141 of theanisotropic holographic screen 140 is gathered at any one point on anoptical axis OX. For example, the diffusion central angle β may bebetween about 10 degrees and about 20 degrees at an edge of the firstsurface 141 of the anisotropic holographic screen 140.

Also, a diffusion angle α at which light is reflected and diffused fromany one point on the first surface 141 of the anisotropic holographicscreen 140 may be, for example, within about 10 degrees. Here, thediffusion angle α may be defined as an angle between a progressiondirection of light diffused at a half intensity of an intensity of thelight diffused at the diffusion central angle β, and the normal lineperpendicular to the first surface 141. According to an exampleembodiment, the diffusion angle α at which light is reflected anddiffused is relatively less, and thus, loss of light may be less. Also,the diffusion central angle β is symmetrically inclined based on thecenter of the first surface 141 of the anisotropic holographic screen140, and thus, an angle of view for the first image L10 may beincreased.

FIGS. 5 and 6 are schematic cross-sectional views illustratingoperations of related diffusion screens. First, referring to FIG. 5 ,the diffusion central angle is constant in all areas of the diffusionscreen. Also, the diffusion screen illustrated in FIG. 5 has arelatively small diffusion angle. As illustrated in FIG. 5 , when thediffusion screen having a small diffusion angle is observed through alens, a viewing window through which the first image L10 may be observedmay be decreased. Further, as indicated by a dotted-line circle in FIG.5 , light that is far from the center of the diffusion screen does notpass through the lens, and thus, an angle of view for the first imageL10 may also be decreased.

Also, referring to FIG. 6 , the diffusion central angle is constant inall areas of the diffusion screen. Also, the diffusion screenillustrated in FIG. 6 has a relatively large diffusion angle comparedwith the diffusion screen illustrated in FIG. 5 . As illustrated in FIG.6 , when the diffusion screen having a large diffusion angle is observedthrough a lens, a viewing window through which the first image L10 maybe observed may be increased. However, when the diffusion angle of thediffusion screen is increased, a degree of transmittance is decreased sothat the second image L20 may be darkened. Also, as indicated by adotted-line circle in FIG. 6 , light diffused toward the outside of thediffusion screen from an area far from the center of the diffusionscreen does not pass through the lens, and thus, due to loss of thelight, the first image L10 may also be darkened.

However, according to the example embodiment, by using the anisotropicholographic screen 140 having different diffusion central angles β basedon locations of the anisotropic holographic screen 140, the angle ofview for the first image L10 may be increased. For example, when thediffusion central angle β at both ends of the anisotropic holographicscreen 140 is 15 degrees, an angle of view of about 90 degrees may beobtained. Also, since the diffusion angle α of the anisotropicholographic screen 140 is about 10 degrees, which is relatively small,the loss of light may be decreased to increase the brightness of thefirst and second images L10 and L20. Thus, the multi-image displayapparatus 100 described above may reduce a difference between the angleof view of the multi-image display apparatus 100 and an actual externalscene, thereby providing a more realistic AR experience. Also, thepolarization selective lens 160 and the anisotropic holographic screen140 may be arranged in front of a user's eye without a relay opticalsystem, and thus, the size of the multi-image display apparatus 100 maybe reduced.

FIG. 7 is a schematic view illustrating a configuration formanufacturing the anisotropic holographic screen 140 of the multi-imagedisplay apparatus 100 illustrated in FIG. 1 . Referring to FIG. 7 , atransparent diffusion plate 10 is arranged above an upper surface of aphotosensitive member 140′ and a convex lens 20 is arranged above thetransparent diffusion plate 10. Thereafter, reference waves are slantlyirradiated toward a lower surface of the photosensitive member 140′ atan angle from a direction normal to the lower surface, and signal wavesare perpendicularly irradiated onto the convex lens 20. Then, the signalwaves are focused by the convex lens 20 and diffused by the transparentdiffusion plate 10. Thus, while the signal waves have a directionalityof being focused by the convex lens 20, the signal waves are diffused bythe transparent diffusion plate 10 and incident into the photosensitivemember 140′.

Here, the reference waves and the signal waves have the same wavelength.For example, light generated from one light source may be split by abeam splitter to be provided as each of reference waves and signalwaves. Then, interference patterns generated when the signal waves andthe reference waves interfere with each other may be recorded in thephotosensitive member 140′. When the photosensitive member 140′ in whichthe interference patterns are recorded is developed, the anisotropicholographic screen 140 performing the operation illustrated in FIG. 4may be formed.

Referring to FIG. 1 , the multi-image display apparatus 100 may beconfigured such that the first image L10 is slantly incident into thefirst surface 141 of the anisotropic holographic screen 140 at an anglewith respect to the direction normal to the first surface. Theanisotropic holographic screen 140 may operate as a reflection diffusionplate only for light incident at the same angle as the reference wavesillustrated in FIG. 7 and may transmit other light without change anddistortion. Thus, when the anisotropic holographic screen 140 ismanufactured, the multi-image display apparatus 100 may be configuredsuch that the first image L10 is incident into the first surface 141 ofthe anisotropic holographic screen 140 at the same incident angle as thereference waves. Then, after the first image L10 is reflected anddiffused by the anisotropic holographic screen 140, the first image L10is focused by the polarization selective lens 160. The second image L20perpendicularly incident into the second surface 142 of the anisotropicholographic screen 140 may pass through the anisotropic holographicscreen 140 and the polarization selective lens 160 without change anddistortion.

Meanwhile, the anisotropic holographic screen 140 may operate as thereflection diffusion plate only for light having the same wavelength asthe reference waves and the signal waves used for manufacturing theanisotropic holographic screen 140. Thus, when the first image L10 has ared image, a green image, and a blue image, all operations describedwith reference to FIG. 7 may be performed with respect to the threewavelength ranges. For example, FIGS. 8 through 10 are schematic viewsillustrating a configuration for manufacturing the anisotropicholographic screen 140 when the first image L10 has the red image, thegreen image, and the blue image.

First, as illustrated in FIG. 8 , reference waves of a red wavelengthrange are slantly irradiated toward the lower surface of thephotosensitive member 140′ and signal waves of the red wavelength rangeare perpendicularly irradiated onto the convex lens 20. Then,interference patterns generated due to the signal waves of the redwavelength range and the reference waves of the red wavelength rangeinterfering with each other are recorded in the photosensitive member140′. Then, as illustrated in FIG. 9 , reference waves of a greenwavelength range are slantly irradiated toward the lower surface of thephotosensitive member 140′ and signal waves of the green wavelengthrange are perpendicularly irradiated onto the convex lens 20, andinterference patterns generated due to the signal waves of the greenwavelength range and the reference waves of the green wavelength rangeinterfering with each other are recorded in the photosensitive member140′. Also, as illustrated in FIG. 10 , reference waves of a bluewavelength range are slantly irradiated toward the lower surface of thephotosensitive member 140′ and signal waves of the blue wavelength rangeare perpendicularly irradiated onto the convex lens 20, and interferencepatterns generated due to the signal waves of the blue wavelength rangeand the reference waves of the blue wavelength range interfering witheach other are recorded in the photosensitive member 140′. Thereafter,the photosensitive member 140′ may be developed to form the anisotropicholographic screen 140. Here, the order in which the reference waves andthe signal waves of each of the red, green, and blue wavelength rangesare irradiated may be arbitrarily selected. Angles at which thereference waves of the red wavelength range, the reference waves of thegreen wavelength range, and the reference waves of the blue wavelengthrange are incident toward the lower surface of the photosensitive member140′ may be the same.

FIG. 11 is a schematic view illustrating a configuration of amulti-image display apparatus 200 according to an example embodiment.Referring to FIG. 11 , the multi-image display apparatus 200 may includea first wavelength-selective anisotropic holographic screen 140 a, asecond wavelength-selective anisotropic holographic screen 140 b, and athird wavelength-selective anisotropic holographic screen 140 c that aresequentially arranged. Other aspects of the multi-image displayapparatus 200 are the same as the aspects of the multi-image displayapparatus 100 illustrated in FIG. 1 .

The first wavelength-selective anisotropic holographic screen 140 a, thesecond wavelength-selective anisotropic holographic screen 140 b, andthe third wavelength-selective anisotropic holographic screen 140 c mayoperate as screens for light of different wavelengths. For example, thefirst wavelength-selective anisotropic holographic screen 140 a mayreflect and diffuse light of a red wavelength and transmit light ofother wavelengths. The second wavelength-selective anisotropicholographic screen 140 b may reflect and diffuse light of a greenwavelength and transmit light of other wavelengths. The thirdwavelength-selective anisotropic holographic screen 140 c may reflectand diffuse light of a blue wavelength and transmit light of otherwavelengths.

Thus, a red image of the first image L10 provided by the image formingdevice 110 is reflected and diffused by the first wavelength-selectiveanisotropic holographic screen 140 a. A green image passes through thefirst wavelength-selective anisotropic holographic screen 140 a, andthen is reflected and diffused by the second wavelength-selectiveanisotropic holographic screen 140 b. A blue image passes through thefirst wavelength-selective anisotropic holographic screen 140 a and thesecond wavelength-selective anisotropic holographic screen 140 b, andthen is reflected and diffused by the third wavelength-selectiveanisotropic holographic screen 140 c. Thereafter, the red image, thegreen image, and the blue image of the first image L10 are focused bythe polarization selective lens 160. The second image L20 passes throughall of the first wavelength-selective anisotropic holographic screen 140a, the second wavelength-selective anisotropic holographic screen 140 b,and the third wavelength-selective anisotropic holographic screen 140 c,and then passes through the polarization selective lens 160.

FIGS. 12 through 14 are schematic views illustrating a configuration formanufacturing the first wavelength-selective anisotropic holographicscreen 140 a, the second wavelength-selective anisotropic holographicscreen 140 b, and the third wavelength-selective anisotropic holographicscreen 140 c of the multi-image display apparatus 100 illustrated inFIG. 11 . First, referring to FIG. 12 , reference waves of a redwavelength range are slantly irradiated toward the lower surface of afirst photosensitive member 140 a′ and signal waves of the redwavelength range are perpendicularly irradiated onto the convex lens 20.Also, interference patterns that are generated when the signal waves ofthe red wavelength range and the reference waves of the red wavelengthrange interfere with each other are recorded in the first photosensitivemember 140 a′. Thereafter, the first photosensitive member 140 a′ may bedeveloped to form the first wavelength-selective anisotropic holographicscreen 140 a.

Also, referring to FIG. 13 , reference waves of a green wavelength rangeare slantly irradiated toward a lower surface of a second photosensitivemember 140 b′ and signal waves of the green wavelength range areperpendicularly irradiated onto the convex lens 20. Also, interferencepatterns that are generated when the signal waves of the greenwavelength range and the reference waves of the green wavelength rangeinterfere with each other are recorded in the second photosensitivemember 140 b′. Thereafter, the second photosensitive member 140 b′ maybe developed to form the second wavelength-selective anisotropicholographic screen 140 b.

Lastly, referring to FIG. 14 , reference waves of a blue wavelengthrange are slantly irradiated toward a lower surface of a thirdphotosensitive member 140 c′ and signal waves of the blue wavelengthrange are perpendicularly irradiated onto the convex lens 20. Also,interference patterns that are generated when the signal waves of theblue wavelength range and the reference waves of the blue wavelengthrange interfere with each other are recorded in the third photosensitivemember 140 c′. Thereafter, the third photosensitive member 140 c′ may bedeveloped to form the third wavelength-selective anisotropic holographicscreen 140 c.

In FIGS. 12 through 14 , all of an angle at which the reference waves ofthe red wavelength range are incident toward the lower surface of thefirst photosensitive member 140 a′, an angle at which the referencewaves of the green wavelength range are incident toward the lowersurface of the second photosensitive member 140 b′, and an angle atwhich the reference waves of the blue wavelength range are incidenttoward the lower surface of the third photosensitive member 140 c′ maybe the same. Also, the first image L10 may be incident onto each of thefirst wavelength-selective anisotropic holographic screen 140 a, thesecond wavelength-selective anisotropic holographic screen 140 b, andthe third wavelength-selective anisotropic holographic screen 140 c atthe same incident angle as these reference waves.

The first wavelength-selective anisotropic holographic screen 140 a, thesecond wavelength-selective anisotropic holographic screen 140 b, andthe third wavelength-selective anisotropic holographic screen 140 c maybe arranged to offset or reduce chromatic aberration of the polarizationselective lens 160. In general, the geometric phase lenses 160 a and 160c of the polarization selective lens 160 are realized by formingpatterns of a plurality of nonlinear material elements on a transparentsubstrate, whereby the polarization selective lens 160 may havechromatic aberration due to dispersion based on the wavelengths. Unlikea general refractive lens having a focal distance that is proportionalto the wavelength, the polarization selective lens 160 using diffractionhas a focal distance that is inversely proportional to the wavelength oflight. That is, as the wavelength of incident light is increased, thefocal distance of the polarization selective lens 160 is decreased, andthe focal distance of the polarization selective lens 160 is sensitivelychanged as the wavelength is changed. For example, the polarizationselective lens 160 may have a first focal distance for a red image, asecond focal distance that is greater than the first focal distance fora green image, and a third focal distance that is greater than thesecond focal distance for a blue image.

According to the example embodiment, the chromatic aberration of thepolarization selective lens 160 may be offset by allowing each of thered image, the green image, and the blue image to have a differentoptical path length by placing the first wavelength-selectiveanisotropic holographic screen 140 a, the second wavelength-selectiveanisotropic holographic screen 140 b, and the third wavelength-selectiveanisotropic holographic screen 140 c on different locations of theoptical path. For example, the first wavelength-selective anisotropicholographic screen 140 a, the second wavelength-selective anisotropicholographic screen 140 b, and the third wavelength-selective anisotropicholographic screen 140 c may be sequentially arranged away from thepolarization selective lens 160. Then, the red image may have a firstoptical path length, the green image may have a second optical pathlength that is greater than the first optical path length, and the blueimage may have a third optical path length that is greater than thesecond optical path length. To this end, the locations of the firstwavelength-selective anisotropic holographic screen 140 a, the secondwavelength-selective anisotropic holographic screen 140 b, and the thirdwavelength-selective anisotropic holographic screen 140 c may beselected by taking into account chromatic aberration of the polarizationselective lens 160 to offset the chromatic aberration.

FIG. 15 is a schematic view illustrating a configuration of amulti-image display apparatus 300 according to an example embodiment.Referring to FIG. 15 , the multi-image display apparatus 300 furtherincludes a light guide plate 170 arranged between the anisotropicholographic screen 140 and the polarization selective lens 160. Thelight guide plate 170 may include an input coupler 171 configured toslantly reflect incident light and provide the incident light into thelight guide plate 170. By using the light guide plate 170, a light pathmay be more easily curved in a small space and it may be possible totransmit light into a small space, and thus, the total size of themulti-image display apparatus 300 may further be decreased.

According to the example embodiment of the multi-image display apparatus300 illustrated in FIG. 15 , the first image L10 generated in the imageforming device 110 may be provided to the anisotropic holographic screen140 through the light guide plate 170. To this end, the collimating lens130 is arranged to provide the first image L10 to the input coupler 171of the light guide plate 170. The first image L10 slantly provided intothe light guide plate 170 by the input coupler 171 may be totallyreflected from an upper surface and a lower surface of the light guideplate 170 and may travel in the light guide plate 170. In this process,a portion of the first image L10 incident into the upper surface of thelight guide plate 170 may be reflected and diffused by the anisotropicholographic screen 140 and may be incident into the polarizationselective lens 160. To this end, the anisotropic holographic screen 140may be arranged to directly contact the upper surface of the light guideplate 170. The second image L20 passes through all of the anisotropicholographic screen 140, the light guide plate 170, and the polarizationselective lens 160. In the example of FIG. 15 , the angle at which theinput coupler 171 provides the incident light into the light guide plate170 is selected to be the same as an incident angle of the referencewaves for manufacturing the anisotropic holographic screen 140.

FIG. 16A is a schematic view illustrating a configuration of amulti-image display apparatus 400 a according to an example embodiment.Referring to FIG. 16A, the multi-image display apparatus 400 a mayinclude the first wavelength-selective anisotropic holographic screen140 a, the second wavelength-selective anisotropic holographic screen140 b, and the third wavelength-selective anisotropic holographic screen140 c that are sequentially arranged. Other aspects of the multi-imagedisplay apparatus 400 a are the same as the aspects of the multi-imagedisplay apparatus 300 illustrated in FIG. 15 . Also, the configurationand operation of the first wavelength-selective anisotropic holographicscreen 140 a, the second wavelength-selective anisotropic holographicscreen 140 b, and the third wavelength-selective anisotropic holographicscreen 140 c may be the same as the configuration and operationaccording to the example embodiments described with reference to FIGS.11 through 14 .

Also, FIG. 16B is a schematic view illustrating a configuration of amulti-image display apparatus 400 b according to an example embodiment.Referring to FIG. 16B, the first wavelength-selective anisotropicholographic screen 140 a, the second wavelength-selective anisotropicholographic screen 140 b, and the third wavelength-selective anisotropicholographic screen 140 c may be located in the light guide plate 170.Other aspects of the multi-image display apparatus 400 b may be the sameas the aspects of the multi-image display apparatus 400 a illustrated inFIG. 16A. FIG. 16B illustrates that an upper surface of the thirdwavelength-selective anisotropic holographic screen 140 c arranged onthe uppermost region and the upper surface of the light guide plate 170correspond to each other. However, all of the first wavelength-selectiveanisotropic holographic screen 140 a, the second wavelength-selectiveanisotropic holographic screen 140 b, and the third wavelength-selectiveanisotropic holographic screen 140 c may be completely buried in thelight guide plate 170.

FIG. 17 is a schematic view illustrating a configuration of amulti-image display apparatus 500 according to an example embodiment.Referring to FIG. 17 , the multi-image display apparatus 500 accordingto the example embodiment may include the image forming device 110configured to form the first image L10, a polarization selective screen183 configured to reflect and diffuse the first image L10 and transmitthe second image L20, the light guide plate 170 configured to providethe first image L10 to the polarization selective screen 183, and thepolarization selective lens 160 configured to focus the first image L10and transmit the second image L20 without refraction. Also, themulti-image display apparatus 500 may further include the collimatinglens 130 configured to collimate the first image L10 formed by the imageforming device 110 and provide the first image L10 to the input coupler171 of the light guide plate 170.

According to the example embodiment, the polarization selective screen183 is configured to operate as a diffusion plate or a transparent flatplate based on a linear polarization direction of incident light. Forexample, FIGS. 18 and 19 are schematic views illustrating an operationof the polarization selective screen 183 illustrated in FIG. 17 . First,referring to FIG. 18 , the polarization selective screen 183 may reflectand diffuse the first image L10 having a first linear polarizationcomponent. Also, referring to FIG. 19 , the polarization selectivescreen 183 may transmit the second image L20 having a second linearpolarization component perpendicular to the first linear polarizationcomponent.

To this end, the multi-image display apparatus 500 may further include afirst linear polarization plate 181 configured to transmit only lighthaving the first linear polarization component and a second linearpolarization plate 182 configured to transmit only light having thesecond liner polarization component. The first linear polarization plate181 is arranged on a light path of the first image L10 that is betweenthe image forming device 110 and the light guide plate 170, so that thefirst image L10 has the first linear polarization component. The secondlinear polarization plate 182 is arranged to face a surface of thepolarization selective screen 183, on which the second image L20 isincident, so that the second image L20 has the second linearpolarization component.

Also, the polarization selective lens 160 focuses the incident light ortransmits the incident light without refraction according to a circularpolarization state of the incident light, and thus, the multi-imagedisplay apparatus 500 may further include a ¼ wavelength plate 184arranged between the light guide plate 170 and the polarizationselective lens 160. Then, a phase of the first image L10 having thefirst linear polarization component is delayed by a ¼ wavelength by the¼ wavelength plate 184, and thus, the first image L10 incident into thepolarization selective lens 160 may have the first circular polarizationcomponent. Also, a phase of the second image L20 having the secondlinear polarization component is delayed by a ¼ wavelength by the ¼wavelength plate 184, and thus, the second image L20 incident into thepolarization selective lens 160 may have the second circularpolarization component.

FIG. 20 is a schematic view illustrating a configuration of amulti-image display apparatus 600 according to an example embodiment.The multi-image display apparatus 600 includes a first linearpolarization plate 181 and a second linear polarization plate 184. Also,the multi-image display apparatus 600 includes the polarizationselective screen 183 configured to reflect and diffuse the first imageL10 having the first linear polarization component and to intactlytransmit the second image L20 having the second linear polarizationcomponent without change. Also, the multi-image display apparatus 600further includes the ¼ wavelength plate 184 arranged between thepolarization selective screen 183 and the polarization selective lens160.

Also, in the multi-image display apparatus 100 illustrated in FIG. 1 ,the first circular polarization plate 120 and the second circularpolarization plate 150 may be replaced by the first linear polarizationplate 181 and the second linear polarization plate 184. Also, themulti-image display apparatus 100 may be configured to further includethe ¼ wavelength plate 184 between the anisotropic holographic screen140 and the polarization selective lens 160.

FIGS. 21 through 23 illustrate various electronic devices to which themulti-image display apparatuses according to example embodimentsdescribed above are applicable. As illustrated in FIGS. 21 through 23 ,at least one of the multi-image display apparatuses of the exampleembodiments may constitute wearable devices. For example, themulti-image display apparatuses may be applied to wearable devices. Forexample, the multi-image display apparatuses may be applied to headmounted displays (HMDs). In addition, the multi-image displayapparatuses may be applied to glasses-type displays or goggle-typedisplays. The wearable electronic devices shown in FIGS. 21 through 23may be operated in an interacting relationship with smartphones.

In addition, the multi-image display apparatuses of the exampleembodiments may be included in smartphones, and the smart phones may beused as multi-image display apparatuses. For example, the multi-imagedisplay apparatuses may be applied to compact electronic devices ormobile electronic devices. The application fields of the multi-imagedisplay apparatuses of the example embodiments may vary in various ways.For example, the multi-image display apparatuses of the exampleembodiments may be not only used to implement AR or MR, but also used inother fields. For example, the technical concepts of the exampleembodiments may be applied not only to AR or MR, but also to displaysthrough which a plurality of images may be simultaneously seen.

It should be understood that the multi-image display apparatusesincluding the polarization selective lens and the screen describedaccording to example embodiments should be considered in a descriptivesense only and not for purposes of limitation. Descriptions of featuresor aspects within each example embodiment should typically be consideredas available for other similar features or aspects in other exampleembodiments. While example embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope as defined by thefollowing claims.

What is claimed is:
 1. A multi-image display apparatus comprising: animage forming device configured to form an image; a first polarizationplate configured to transmit a first polarization component of the imageprovided from the image forming device; a second polarization plateconfigured to transmit a second polarization component of external lightthat is provided from a path different from the image, the secondpolarization component being different from the first polarizationcomponent; a screen configured to reflect and diffuse the image, andtransmit the external light; a polarization selective lens configured tofocus the image having the first polarization component, and transmitthe external light having the second polarization component withoutrefraction; and a light guide plate disposed between the screen and thepolarization selective lens, wherein the light guide plate is configuredto provide the image coming from the image forming device to the screenthrough total reflection.
 2. The multi-image display apparatus of claim1, wherein the screen comprises a first surface and a second surfacethat is opposite to the first surface, and wherein the screen furthercomprises an anisotropic holographic screen configured to reflect anddiffuse light that is incident on the first surface at an angle, andtransmit light incident on the second surface.
 3. The multi-imagedisplay apparatus of claim 2, wherein the image forming device isdisposed to provide the image to the first surface of the screen at anangle.
 4. The multi-image display apparatus of claim 2, wherein thesecond polarization plate is disposed on the second surface of thescreen.
 5. The multi-image display apparatus of claim 2, wherein thescreen is configured such that a diffusion central angle is 0 degreesfrom a normal line perpendicular to the first surface in a central areaof the first surface, and the diffusion central angle increases from thenormal line perpendicular to the first surface from the central area ofthe first surface to edge areas of the first surface.
 6. The multi-imagedisplay apparatus of claim 5, wherein the screen is configured such thatthe diffusion central angle is symmetrically inclined based on thecentral area of the first surface, and light reflected and diffused atthe diffusion central angle from the first surface are gathered on apoint of an optical axis.
 7. The multi-image display apparatus of claim5, wherein the diffusion central angle ranges from 10 degrees to 20degrees at an edge of the first surface.
 8. The multi-image displayapparatus of claim 5, wherein a diffusion angle at which light isreflected and diffused from the first surface is within 10 degrees.
 9. Amulti-image display apparatus comprising: an image forming deviceconfigured to form an image; a first polarization plate configured totransmit a first polarization component of the image provided from theimage forming device; a second polarization plate configured to transmita second polarization component of external light that is provided froma path different from the image, the second polarization component beingdifferent from the first polarization component; a screen configured toreflect and diffuse the image, and transmit the external light; apolarization selective lens configured to focus the image having thefirst polarization component, and transmit the external light having thesecond polarization component without refraction; and a light guideplate disposed between the screen and the polarization selective lens,wherein the image comprises a first color image, a second color image,and a third color image, and wherein the screen comprises: a firstanisotropic holographic screen configured to reflect and diffuse thefirst color image that is incident on a first surface of the firstanisotropic holographic screen at an angle, and transmit light incidenton a second surface of the first anisotropic holographic screen that isopposite to the first surface; a second anisotropic holographic screenconfigured to reflect and diffuse the second color image that isincident on a third surface of the second anisotropic holographic screenat an angle, and transmit light incident on a fourth surface of thesecond anisotropic holographic screen that is opposite to the thirdsurface; and a third anisotropic holographic screen configured toreflect and diffuse the third color image that is incident on a fifthsurface of the third anisotropic holographic screen at an angle, andtransmit light incident on a sixth surface of the third anisotropicholographic screen that is opposite to the fifth surface.
 10. Themulti-image display apparatus of claim 9, wherein the image formingdevice is configured to provide the first color image to the firstsurface of the first anisotropic holographic screen at an angle, providethe second color image to the third surface of the second anisotropicholographic screen at an angle, and provide the third color image to thefifth surface of the third anisotropic holographic screen at an angle.11. The multi-image display apparatus of claim 9, wherein the firstanisotropic holographic screen is configured to transmit the secondcolor image and the third color image incident on the first surface, thesecond anisotropic holographic screen is configured to transmit thefirst color image and the third color image incident on the thirdsurface, and the third anisotropic holographic screen is configured totransmit the first color image and the second color image incident onthe fifth surface.
 12. The multi-image display apparatus of claim 9,wherein the first anisotropic holographic screen is configured such thata diffusion central angle of the first color image is 0 degrees from anormal line perpendicular to the first surface, in a central area of thefirst surface, and the diffusion central angle of the first color imagefrom the normal line perpendicular to the first surface increases fromthe central area of the first surface to edge areas of the firstsurface, the second anisotropic holographic screen is configured suchthat a diffusion central angle of the second color image is 0 degreesfrom a normal line perpendicular to the third surface in a central areaof the third surface, and the diffusion central angle of the secondcolor image from the normal line perpendicular to the third surfaceincreases from the central area of the third surface to edge areas ofthe third surface, and the third anisotropic holographic screen isconfigured such that a diffusion central angle of the third color imageis 0 degrees from a normal line perpendicular to the fifth surface in acentral area of the fifth surface, and the diffusion central angle ofthe third color image from the normal line perpendicular to the fifthsurface increases from the central area of the fifth surface to edgeareas of the fifth surface.
 13. The multi-image display apparatus ofclaim 9, wherein the first anisotropic holographic screen, the secondanisotropic holographic screen, and the third anisotropic holographicscreen are sequentially disposed away from the polarization selectivelens, such that the first color image has a first light path length, thesecond color image has a second light path length greater than the firstlight path length, and the third color image has a third light pathlength greater than the second light path length, and wherein the firstanisotropic holographic screen, the second anisotropic holographicscreen, and the third anisotropic holographic screen are disposed tooffset chromatic aberration of the polarization selective lens.
 14. Amulti-image display apparatus comprising: an image forming deviceconfigured to form an image; a first polarization plate configured totransmit a first polarization component of the image provided from theimage forming device; a second polarization plate configured to transmita second polarization component of external light that is provided froma path different from the image, the second polarization component beingdifferent from the first polarization component; a screen configured toreflect and diffuse the image, and transmit the external light; apolarization selective lens configured to focus the image having thefirst polarization component, and transmit the external light having thesecond polarization component without refraction; and a light guideplate disposed between the screen and the polarization selective lens,wherein the light guide plate comprises an input coupler configured toreflect incident light at an angle, and to provide the incident lightinto the light guide plate, and wherein the image forming device isdisposed to provide the image to the input coupler of the light guideplate.
 15. The multi-image display apparatus of claim 14, wherein thelight guide plate is configured to totally reflect the image provided atan angle to the light guide plate by the input coupler, between a firstsurface of the light guide plate and a second surface of the light guideplate that is opposite to the first of the light guide plate, and thescreen is directly disposed on the first surface of the light guideplate.
 16. The multi-image display apparatus of claim 1, wherein thepolarization selective lens is configured to focus light having a firstcircular polarization component having a first rotation direction andtransmit, without change, light having a second circular polarizationcomponent having a second rotation direction which is opposite to thefirst rotation direction.
 17. The multi-image display apparatus of claim16, wherein the polarization selective lens comprises two geometricphase lenses and a polarization conversion plate between the twogeometric phase lenses, wherein the two geometric phase lenses areconfigured to operate as convex lenses with respect to the light havingthe first circular polarization component, and operate as concave lenseswith respect to the light having the second circular polarizationcomponent, and wherein the polarization conversion plate is configuredto transmit, without change, the light having the first circularpolarization component, and convert the light having the second circularpolarization component into the light having the first circularpolarization component.
 18. The multi-image display apparatus of claim16, wherein the first polarization plate comprises a first circularpolarization plate configured to transmit the light having the firstcircular polarization component, and the second polarization platecomprises a second circular polarization plate configured to transmitthe light having the second circular polarization component.
 19. Themulti-image display apparatus of claim 1, wherein the screen comprises apolarization selective screen configured to reflect and diffuse lighthaving a first linear polarization component, and transmit light havinga second linear polarization component that is perpendicular to thefirst linear polarization component, wherein the first polarizationplate comprises a first linear polarization plate configured to transmitthe light having the first linear polarization component, and the secondpolarization plate comprises a second linear polarization plateconfigured to transmit the light having the second linear polarizationcomponent perpendicular to the first linear polarization component, andwherein the multi-image display apparatus further comprises a ¼wavelength plate disposed between the screen and the polarizationselective lens.